Retinoids (e.g. retinol and retinyl esters) are common ingredients used in cosmetic products. Retinol (vitamin A) is an endogenous compound which occurs naturally in the human body and is essential for normal epithelial cell differentiation. Natural and synthetic vitamin A derivatives have been used extensively in the treatment of a variety of skin disorders and have been used as skin repair or renewal agents. Retinoic acid has been employed to treat a variety of skin conditions, e.g., acne, wrinkles, psoriasis, age spots and discoloration. See e.g. Vahlquist, A. et al., J. Invest. Dermatol., Vol. 94, Holland D. B. and Cunliffe, W. J. (1990), pp. 496-498; Ellis, C. N. et. Al., “Treatment of Actinically Aged Skin with Tropical Tretinoin,” S. Karger, Basel Vol. 3, (1989), pp. 249-252; and PCT Patent Application No. WO 93/19743.
Retinol, however, is particularly unstable in cosmetic formulations because retinol can undergo chemical degradation as a consequence of many factors which include oxidation, thermal instability and UV induced degradation. Retinyl esters are also subject to these instabilities although to a lesser extent than retinol. Retinoid benefits on skin can be enhanced by the coapplication of retinoid booster molecules. However, many if not all of the retinoid booster molecules also increase the instability of the retinol. It is necessary therefore to protect retinol formulations containing boosters to a higher degree than is necessary for formulations containing retinol alone.
Several references seek to create stable compositions containing retinol. For example, U.S. Pat. No. 5,976,555 assigned to Johnson & Johnson, discloses skin care compositions comprising oil in water emulsions containing retinoids, an emulsifier system, and a co-emulsifier. The patent describes the use of a container for storing the composition so that the composition is out of contact with oxygen. The container is described for use for the retinoid composition with an emulsifier system and a co-emulsifier alone and does not protect the retinoid from degradation due to contact with retinoid boosters.
U.S. Pat. No. 5,800,596, assigned to L'Oreal, discloses a water in oil emulsion containing retinol in a dispensing device that has walls impermeable to oxygen or UV light and an oxygen trapping device. The patent does not teach or suggest the use of boosters and the problems associated with retinoid stability in the presence of boosters.
None of the references cited above teach or suggest systems for stabilizing retinoid compositions in the presence of retinoid boosters. Therefore, a need still exists for such stable cosmetic compositions containing retinoids and retinoid boosters.